A suburban clinic of Seattle Children’s Hospital is warning patients they could have been exposed to infection by improperly cleaned and sterilized equipment.

Hospital officials said Wednesday that patients who had a surgical procedure at its Bellevue clinic will need to be tested for hepatitis B and C, as well HIV. They say the risk to patients is extremely low.

The hospital is contacting patients and offering a free blood test to those who may be affected.

The Seattle Times reports (http://is.gd/3e5beJ ) as many as 12,000 children and young adults treated at the clinic since 2010 could be at risk of infection from reusable surgical instruments that may not have been properly cleaned.

The instruments were used in a wide range of procedures. The problem was discovered last Thursday during a routine inspection.